workspace: Don't try to use per-workspace MRU lists as a hint for focusing

A prior commit switched from focusing the topmost window as the default
window to focusing the MRU window. This was done in alignment with the
introduction of per-workspace MRU lists to avoid problems where the window
stack was inadvertently changed when focusing windows during window switches.

Now that focusing windows don't have as big an impact on the stacking order,
we can revert back to focusing the top window, which is less confusing to the
user.

For now, leave per-workspace MRU lists, as they're a pretty good approximation
of a global MRU list, and it works well enough.

https://bugzilla.gnome.org/show_bug.cgi?id=620744

Based on commit https://gitlab.gnome.org/GNOME/metacity/-/commit/f628d8f8901f46fa9e00707ae9d7ccfd1e85f427

4 files changed, 17 insertions, 39 deletions

diff --git a/src/core/stack.c b/src/core/stack.c
index fa4dbee3..d2eb7acf 100644
--- a/src/core/stack.c
+++ b/src/core/stack.c
@@ -237,7 +237,6 @@ meta_stack_freeze (MetaStack *stack)
   stack->freeze_count += 1;
 }
 
-
 void
 meta_stack_thaw (MetaStack *stack)
 {
diff --git a/src/core/window.c b/src/core/window.c
index 603bedf3..bc04b644 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -6214,7 +6214,6 @@ idle_update_icon (gpointer data)
   return FALSE;
 }
 
-
 MetaWorkspace *
 meta_window_get_workspace (MetaWindow *window)
 {
@@ -6224,7 +6223,6 @@ meta_window_get_workspace (MetaWindow *window)
     return window->workspace;
 }
 
-
 GList*
 meta_window_get_workspaces (MetaWindow *window)
 {
diff --git a/src/core/workspace.c b/src/core/workspace.c
index 98c33e20..04ba575b 100644
--- a/src/core/workspace.c
+++ b/src/core/workspace.c
@@ -33,7 +33,7 @@
 
 void meta_workspace_queue_calc_showing   (MetaWorkspace *workspace);
 static void set_active_space_hint        (MetaScreen *screen);
-static void focus_ancestor_or_mru_window (MetaWorkspace *workspace,
+static void focus_ancestor_or_top_window (MetaWorkspace *workspace,
                                           MetaWindow    *not_this_one,
                                           guint32        timestamp);
 static void free_this                    (gpointer candidate,
@@ -971,7 +971,7 @@ meta_workspace_focus_default_window (MetaWorkspace *workspace,
 
   if (meta_prefs_get_focus_mode () == META_FOCUS_MODE_CLICK ||
       !workspace->screen->display->mouse_mode)
-    focus_ancestor_or_mru_window (workspace, not_this_one, timestamp);
+    focus_ancestor_or_top_window (workspace, not_this_one, timestamp);
   else
     {
       MetaWindow * window;
@@ -1008,7 +1008,7 @@ meta_workspace_focus_default_window (MetaWorkspace *workspace,
             }
         }
       else if (meta_prefs_get_focus_mode () == META_FOCUS_MODE_SLOPPY)
-        focus_ancestor_or_mru_window (workspace, not_this_one, timestamp);
+        focus_ancestor_or_top_window (workspace, not_this_one, timestamp);
       else if (meta_prefs_get_focus_mode () == META_FOCUS_MODE_MOUSE)
         {
           meta_topic (META_DEBUG_FOCUS,
@@ -1035,13 +1035,11 @@ record_ancestor (MetaWindow *window,
  * window on active workspace
  */
 static void
-focus_ancestor_or_mru_window (MetaWorkspace *workspace,
+focus_ancestor_or_top_window (MetaWorkspace *workspace,
                               MetaWindow    *not_this_one,
                               guint32        timestamp)
 {
   MetaWindow *window = NULL;
-  MetaWindow *desktop_window = NULL;
-  GList *tmp;
 
   if (not_this_one)
     meta_topic (META_DEBUG_FOCUS,
@@ -1072,36 +1070,8 @@ focus_ancestor_or_mru_window (MetaWorkspace *workspace,
         }
     }
 
-  /* No ancestor, look for the MRU window */
-  tmp = workspace->mru_list;
-
-  while (tmp)
-    {
-      MetaWindow* tmp_window;
-      tmp_window = ((MetaWindow*) tmp->data);
-      if (tmp_window != not_this_one           &&
-          meta_window_showing_on_its_workspace (tmp_window) &&
-          tmp_window->type != META_WINDOW_DOCK &&
-          tmp_window->type != META_WINDOW_DESKTOP)
-        {
-          window = tmp->data;
-          break;
-        }
-      else if (tmp_window != not_this_one      &&
-               desktop_window == NULL          &&
-               meta_window_showing_on_its_workspace (tmp_window) &&
-               tmp_window->type == META_WINDOW_DESKTOP)
-        {
-          /* Found the most recently used desktop window */
-          desktop_window = tmp_window;
-        }
-
-      tmp = tmp->next;
-    }
-
-  /* If no window was found, default to the MRU desktop-window */
-  if (window == NULL)
-    window = desktop_window;
+  window = meta_stack_get_default_focus_window (workspace->screen->stack,
+                                                workspace, NULL);
 
   if (window)
     {
diff --git a/src/core/workspace.h b/src/core/workspace.h
index 7d02861e..b8ea3c97 100644
--- a/src/core/workspace.h
+++ b/src/core/workspace.h
@@ -52,6 +52,17 @@ struct _MetaWorkspace
   MetaScreen *screen;
 
   GList *windows;
+  
+  /* The "MRU list", or "most recently used" list, is a list of
+   * MetaWindows ordered based on the time the the user interacted
+   * with the window most recently.
+   *
+   * For historical reasons, we keep an MRU list per workspace.
+   * It used to be used to calculate the default focused window,
+   * but isn't anymore, as the window next in the stacking order
+  * can sometimes be not the window the user interacted with last,
+  */
+
   GList *mru_list;
 
   GList  *list_containing_self;